animal phs 15

gases

what are extensions of the body surface?

the lungs, gills, and gut

what are the secretions of the lungs, gills, and gut?

exocrine (enzymes, salts, and carbs) and endocrine (hormones)

what is the function of gas transfer systems in vertebrates?

the absorption of O2 and the elimination of CO2

describe the respiratory epithelium in the lungs and gills.

it is a thin layer of cells about 5-15 micrometers thick, it is a major portion of the total body surface area about 50-100 meters squared in humans

what are the three components of the gas transfer systems in vertebrates?

fluid (air or water), fluid pump (lungs or gills), and blood pump (heart chambers)

what are the four functions of the three components of the gas transfer systems in vertebrates?

the breathing movements that provide continuous supply of the fluid, the diffusion of gases across the respiratory epithelium, the transport of gases in the circulatory system, and the diffusion of gasses from the blood to the tissues

what is daltons law?

the partial pressure of each gas in a mixture is independent from other gases present so that the total pressure equals the sum of the partial pressures of all the gasses present. the partial pressure of gas in a mixture depends on the number of molecules present in a given volume at a given temperature

give an example of daltons law for the partial pressure of oxygen in dry air at sea level.

oxygen accounts for 20.95% of all gas molecules in dry air and the standard sea level air pressure is 760 mmHg. so 760 × 0.2095 = 159 mmHg

what is henrys law?

the quantity of a gas that dissolves in a liquid at a given temperature is proportional to the partial pressure of that gas in the gas phase. the quantity of a gas in a liquid equals aP where P is the partial pressure of the gas in the gas phase and a is the bunsen solubility coefficient which is independent of P

what is the role of hemoglobin in vertebrates?

it is the main respiratory pigment (bright red when carrying O2 and brown when not) 

describe the solubility of O2 in blood.

it is high due to hemoglobin

describe the O2 content at normal arterial pressure.

plasma alone is at 0.3% volume and arterial blood with hemoglobin is at 20% volume (number of O2 molecules that would be present in 20ml of air, dissolved in 100ml of blood)

where is hemoglobin found?

inside red blood cells (erythrocytes)

describe the structure of hemoglobin.

there is two globin heterodimers a1b1 and a2b2.

what does the O2 bind to on the heme cofactor and what does it do?

it binds to the central iron atom and it is cooperative so the binding of O2 to the first four subunits facilitates the binding of O2 to the next three (increases the affinity of hemoglobin for O2) resulting in a sigmoid oxygen-hemoglobin dissociation curve

what is myoglobin?

a protein that stores O2 in muscle cells and is similar in structure to a single globin

what is the oxygen-hemoglobin dissociation curve?

a graphical representation of the relationship between the amount of oxygen bound to hemoglobin and the partial pressure of oxygen in the blood.

what do the hemoglobin and myoglobin curves look like?

hemoglobin is a sigmoid curve and myoglobin is a hyperbolic curve

what is p50?

the partial pressure of O2 at which hemoglobin or myoglobin are 50% saturated with O2. myoglobin has a higher affinity fir O2 than hemoglobin so a lower air pO2 is sufficient for 50% saturation

what is po2?

the partial pressure of O2 in blood

what do genetic variations in the protein structure of the globins cause?

variations in the affinity of hemoglobin for O2

when does the composition of hemoglobin vary?

during development to meet the special gas transfer and pH regulation requirements at each stage. r globin (fetal) has a higher affinity for O2 than b globin (adult) to enhance oxygen transfer from mother to fetus

what occurs to the proportions of fetal and adult hemoglobin during birth?

the proportion of fetal hemoglobin decreases and adult hemoglobin increases, so the oxygen affinity of blood decreases (and a higher p50)

what happens to the affinity of hemoglobin for O2 in someone with sickle cell anemia?

a glutamic acid in B globin is replaced with valine, reducing the affinity of hemoglobin for O2 and impairing the solubility and absorption of oxygen. the polypeptide forms large polymers that distort the shape of red blood cells, affecting blood flow and oxygen transport

what four environmental factors can reduce the affinity of hemoglobin for O2?

an increase in temperature, a decrease in pH (the Bohr effect), an increase in CO2 concentration, and the binding of organic phosphate ligands (BPG, ATP, or GTP) to the globins. any of these shifts the dissociation curve towards the right

how does the pH become lowered?

CO2 reacts with water to produce carbonic acid (H2CO3) which quickly dissociates causing a lower affinity of hemoglobin for oxygen

describe the O2 saturation of hemoglobin in the systemic veins.

it is lower because there is a higher CO2 content

what additionally reduces its affinity for O2?

Co2 binds to the terminal amino groups in hemoglobin

what occurs to the affinity of hemoglobin for O2 at the tissues with high pH?

CO2 entering the blood lowers the pH and induces the unloading of O2 from Hb to the tissues and the loading of Co2 to Hb

what occurs to the affinity of hemoglobin for O2 at the respiratory surface with high pH?

CO2 is unloaded and released to the environment, raising the blood pH and promoting the binding og O2 to Hb

what occurs at high altitudes?

low atmospheric O2 results in the acceleration of breathing causing a decrease in blood CO2 and a sustained high affinity of hemoglobin for O2. resulting in BPG levels increasing to offset the effect of low blood CO2

when do BPG levels increase additionally?

during pregnancy

what five forms do CO2 exist in the blood as?

carbon dioxide (reacts with water to produce ca), carbonic acid (dissociates into bc or c), bicarbonate, carbonate, and carbamino compounds (when CO2 reacts with the terminal amino groups in plasma proteins and Hb inside red blood cells) (protein NHCOO-s including HbCOO-)

what is the major change with the increase in Pco2?

the increase bicarbonate (HCO3- the most abundant form of CO2 in the blood) and carbamino (protein NHCOO-) content in the plasma and inside the erythrocytes. a small amount remains dissolved CO2 

describe the total blood CO2 content in the systemic arteries compared to the systemic veins.

lower Pco2 and total blood CO2 content in systemic arteries than in systemic veins

describe the carbon dioxide bicarbonate buffer system.

generation of bicarbonate generates H+

what two buffer systems maintain stable pH in animals?

the Co2 + OH- = HCO3- at a pH of 6.08 and the NH4+ + H+ = NH3 at a pH of 9.58 (physiological pH of animals is maintained somewhere between the two values)

describe the ratios of the two buffer systems at physiological pH in vertebrates.

the CO2/HCO3- ratio is low indicating low CO2 content and the NH3/NH4+ ratio is also low indicating low NH3 content

what is the CO2 + OH- = HCO3 reaction catalyzed by?

the enzyme carbonic anhydrase which is present in erythrocytes (even though most of the blood bicarbonate is present in the plasma)

where does the conversion of CO2 into bicarbonate occur?

mostly in the erythrocytes, then HCO3- is transferred to the plasma in exchange for Cl-. catalyzed by band III membrane protein and is the rate limiting step for the entire process of gas exchange

describe the exchange of gases between tissues and blood.

CO2 enters the red blood cell and reacts with OH- from the dissociation of H20 to yield HCO3- and H+, this lowers the pH and causes the dissociation of O2 from Hb, the production of HCO3- in the plasma is slow (no enzyme), CO2 also forms HbCOO- forcing the release of O2 from Hb, O2 is delivered to the tissues and HCO3- goes to the plasma

what is the chloride shift?

the exchange of HCO3- for Cl- balances the charges to keep the reaction of CO2 +OH- = HCO3- in the forward direction

what are the results of systemic circulation

CO2 (as waste) goes from tissues to the blood and O2 (from pulmonary circulation) goes from the blood to the tissues

describe the exchange of gases between blood and air between the respiratory epithelium.

the CO2 gradient across the respiratory epithelium (higher CO2 content in the blood) causes CO2 to escape to the atmosphere, shifting the CO2 + OH- reaction in the reverse direction dissociating HbCOO- this results in higher pH allowing O2 to bind to Hb (higher pH higher affinity of Hb for O2). the chloride shift in the opposite direction balances the charges keeping the reaction going in the reverse direction.

what are the results of pulmonary circulation?

CO2 (as waste) goes from blood to the atmosphere and O2 from the air goes to the blood

what occurs as Co2 from the tissues and O2 from the environment pass through the red blood cell membrane?

changes in the pH inside the cell facilitate the uptake or release of O2

what causes an increase in H+ (decrease in pH)?

an increase in CO2 and its conversion to HCO3- causing the release of O2 from Hb in the tissues

what causes an increase in pH?

the loss of CO2 through the respiratory epithelium promotes the binding of O2 to hemoglobin